System and method for controlling fuel supplied to an engine

ABSTRACT

Systems and methods for determining fuel delay in a fuel injected engine with cylinders that may be deactivated are presented. In one example, the fuel injection delay is determined via a cylinder firing schedule array when the cylinder firing schedule array is available. The fuel injection delay is determined via weighted average of a fuel injection delay of a present engine cycle and a fuel injection delay of a past engine cycle when the cylinder firing schedule array is not available.

FIELD

The present description relates to a system and methods for supplyingfuel to a variable displacement engine. The system and methods providefor adjusting a fuel delay compensation value responsive to whether ornot fuel is delivered to engine cylinders.

BACKGROUND AND SUMMARY

Fuel may be injected to an internal combustion engine so that the enginemay provide a requested or desired torque. The amount of fuel injectedto the engine may be different than an amount of fuel commanded to beinjected to the engine. Further, the amount of fuel requested to beinjected may be different than an amount of fuel that provides a desiredengine air-fuel mixture ratio. The fueling differences may result fromengine component tolerance variation, sensor measurement errors, anderrors in open loop fuel control parameters. An estimate of engineair-fuel ratio may be determined via an oxygen sensor, and the engineair-fuel ratio may be fed back to an engine controller to compensateerrors between a desired engine air-fuel ratio and a measured air-fuelratio. The controller may determine an engine air-fuel ratio error bysubtracting the measured engine air-fuel ratio from the desired engineair-fuel ratio. The engine air-fuel ratio error may be multiplied by again (e.g., real number) to correct the engine air-fuel ratio error. Ifthe value of the gain is small, a long period of time may be needed todrive the engine air-fuel ratio error toward a value of zero. However,if the gain is made too large, the engine air-fuel ratio may be drivento oscillate about the desired engine air-fuel ratio. The oscillationsmay increase engine emissions and degrade vehicle drivability.

The air-fuel oscillations may be related to a fuel injection delay timebetween when the fuel is injected to a cylinder and a time when itscombustion byproducts are converted into an engine air-fuel ratio viathe oxygen sensor and a transfer function. The fuel injection delay timemay include but is not limited to the time between fuel injection andcombustion of fuel within the cylinder. The delay may also include theamount of time it takes the engine to rotate through the exhaust strokeof the cylinder receiving the fuel and release exhaust gases from thecylinder into the exhaust manifold as well as an amount of time it takesthe exhaust gases to travel from the exhaust valves of the cylinder tothe oxygen sensor in the exhaust manifold. The delay time may cause thecontroller to observe no change in engine air-fuel ratio when the engineair-fuel may have already changed. Consequently, the controller mayattempt to increase the control action (e.g., amount of fuel injected)to drive the measured engine air-fuel ratio closer to the desired engineair-fuel ratio. However, since the engine air-fuel ratio already changeddue to earlier control adjustments, the engine air-fuel ratio may beoverdriven, thereby causing the controller to over compensate in areverse direction, which may induce the engine air-fuel ratiooscillations.

The fuel injection delay time may be empirically determined viaadjusting an air-fuel ratio of engine cylinders at a steady state enginespeed and recording an amount of time it take to observe a change in theengine air-fuel ratio. The delay value may be stored in memory where itrepresents fuel injection time delay for each engine cylinder. The fuelinjection delay value may be applied in a controller compensationnetwork to allow for increased gain while reducing the possibility ofengine air-fuel ratio oscillations. However, recent developments haveenabled each cylinder of an engine to be activated and deactivatedindependent of other cylinders to increase engine efficiency and providea desired amount of torque. Further, the cylinders may be activated anddeactivated in many different combinations to maintain cylindertemperature and reduce engine oil consumption. As a result, a singlevalue for the fuel injection delay estimate for a particular enginespeed and load may no longer be appropriate. Therefore, it may bedesirable to provide a way of determining fuel injection delay for anengine having cylinders that may be deactivated.

The inventors herein have recognized the above-mentioned issues and havedeveloped an engine control method, comprising: injecting fuel to anengine via a controller in response to a fuel injection delay producedvia a weighted average of a fuel injection delay of a past engine cycleand a fuel injection delay of a present engine cycle.

By adjusting a fuel injection delay based on a weighted average of afuel injection delay of a past engine cycle and a fuel injection delayof a present engine cycle, it may be possible to provide the technicalresult of an improved estimate of fuel injection delay when it isunknown whether or not one or more cylinders of a cylinder bank will bedeactivated (e.g., cessation of combustion and fuel injection to theengine cylinder) in the near future. Incorporating past fuel injectiondelays and present fuel injection delay into an estimate of future fuelinjection delay provides a reasonable estimate of future fuel injectiondelays when past cylinder deactivation patterns are correlated to futurecylinder deactivation patterns. In cases where a future cylinderdeactivation pattern is known, the fuel injection delay may bedetermined via adding a base cylinder delay time to an extra delay timethat is based on the expected cylinder deactivation pattern. In theseways, whether or not a future cylinder firing pattern is known, anestimate of fuel injection delay may be determined.

The present description may provide several advantages. In particular,the approach may provide improved fuel injection control by permittinghigher gains so that fuel injection errors may be reduced in a moretimely manner. Further, the approach provides for estimating fuelinjection delay whether or not a future cylinder firing pattern isknown. In addition, the approach may provide improved air-fuel controlfor engines that may deactivate engine cylinders in a large number ofdifferent patterns.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingan example of an embodiment, referred to herein as the DetailedDescription, when taken alone or with reference to the drawings, where:

FIG. 1 is a schematic diagram of an engine;

FIG. 2A is a schematic diagram of an eight cylinder engine with twocylinder banks;

FIG. 2B is a schematic diagram of a four cylinder engine with a singlecylinder bank;

FIG. 3 is a block diagram of a fuel control system for a cylinder bank;

FIGS. 4-6 show a flow chart of an example method for determining andapplying fuel injection delay;

FIG. 7 is an example sequence where fuel injection delay is determined;and

FIG. 8 is an alternate example sequence where fuel injection delay isdetermined.

DETAILED DESCRIPTION

The present description is related to determining fuel injection delayfor an engine that includes cylinders that may be deactivated andreactivated from time to time. The fuel injection delay determiningmethods described herein may be applied to a cylinder bank of an engine.Fuel injection delay times of multiple cylinder bank engines may bedetermined via reproducing the methods for determining fuel injectiontiming for a single bank of cylinders and applying the method to othercylinder banks. An engine cylinder of an engine is shown in FIG. 1. Theengine cylinder of FIG. 1 may be part of an engine that includesmultiple cylinders as shown in FIGS. 2A and 2B. Fuel supplied to a bankof cylinders may be regulated via a controller as shown in FIG. 3. FIGS.4-6 show methods for determining fuel injection delay. FIGS. 7 and 8show example sequences where fuel injection delay is determined.

Referring to FIG. 1, internal combustion engine 10, comprising aplurality of cylinders, one cylinder of which is shown in FIG. 1, iscontrolled by electronic engine controller 12. Engine 10 includescombustion chamber 30 and cylinder walls 32 with piston 36 positionedtherein and connected to crankshaft 40.

Combustion chamber 30 is shown communicating with intake manifold 44 andexhaust manifold 48 via respective intake valve 52 and exhaust valve 54.Each intake and exhaust valve may be operated by an intake cam 51 and anexhaust cam 53. The position of intake cam 51 may be determined byintake cam sensor 55. The position of exhaust cam 53 may be determinedby exhaust cam sensor 57. Intake cam 51 and exhaust cam 53 may be movedrelative to crankshaft 40 via intake valve phase actuator 59 and exhaustvalve phase actuator 58.

Fuel injector 66 is shown positioned to inject fuel directly intocylinder 30, which is known to those skilled in the art as directinjection. Alternatively, fuel may be injected to an intake port, whichis known to those skilled in the art as port injection. Fuel injector 66delivers liquid fuel in proportion to the pulse width of signal fromcontroller 12. Fuel is delivered to fuel injector 66 by a fuel system175. In addition, intake manifold 44 is shown communicating withoptional electronic throttle 62 (e.g., a butterfly valve) which adjustsa position of throttle plate 64 to control air flow from air filter 43and air intake 42 to intake manifold 44. Throttle 62 regulates air flowfrom air filter 43 in engine air intake 42 to intake manifold 44. In oneexample, a high pressure, dual stage, fuel system may be used togenerate higher fuel pressures. In some examples, throttle 62 andthrottle plate 64 may be positioned between intake valve 52 and intakemanifold 44 such that throttle 62 is a port throttle.

Distributorless ignition system 88 provides an ignition spark tocombustion chamber 30 via spark plug 92 in response to controller 12.Universal Exhaust Gas Oxygen (UEGO) sensor 126 is shown coupled toexhaust manifold 48 upstream of catalytic converter 70. Alternatively, atwo-state exhaust gas oxygen sensor may be substituted for UEGO sensor126.

Converter 70 can include multiple catalyst bricks, in one example. Inanother example, multiple emission control devices, each with multiplebricks, can be used. Converter 70 can be a three-way type catalyst inone example.

Controller 12 is shown in FIG. 1 as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106 (e.g., non-transitory memory), random access memory 108, keepalive memory 110, and a conventional data bus. Controller 12 is shownreceiving various signals from sensors coupled to engine 10, in additionto those signals previously discussed, including: engine coolanttemperature (ECT) from temperature sensor 112 coupled to cooling sleeve114; a position sensor 134 coupled to an accelerator pedal 130 forsensing force applied by human driver 132; a measurement of enginemanifold pressure (MAP) from pressure sensor 122 coupled to intakemanifold 44; an engine position sensor from a Hall effect sensor 118sensing crankshaft 40 position; a measurement of air mass entering theengine from sensor 120; brake pedal position from brake pedal positionsensor 154 when human driver 132 applies brake pedal 150; and ameasurement of throttle position from sensor 58. Barometric pressure mayalso be sensed (sensor not shown) for processing by controller 12. In apreferred aspect of the present description, engine position sensor 118produces a predetermined number of equally spaced pulses everyrevolution of the crankshaft from which engine speed (RPM) can bedetermined.

In some examples, the engine may be coupled to an electric motor/batterysystem in a hybrid vehicle. Further, in some examples, other engineconfigurations may be employed, for example a diesel engine.

During operation, each cylinder within engine 10 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54 closes and intake valve 52 opens. Air isintroduced into combustion chamber 30 via intake manifold 44, and piston36 moves to the bottom of the cylinder so as to increase the volumewithin combustion chamber 30. The position at which piston 36 is nearthe bottom of the cylinder and at the end of its stroke (e.g., whencombustion chamber 30 is at its largest volume) is typically referred toby those of skill in the art as bottom dead center (BDC). During thecompression stroke, intake valve 52 and exhaust valve 54 are closed.Piston 36 moves toward the cylinder head so as to compress the airwithin combustion chamber 30. The point at which piston 36 is at the endof its stroke and closest to the cylinder head (e.g., when combustionchamber 30 is at its smallest volume) is typically referred to by thoseof skill in the art as top dead center (TDC). In a process hereinafterreferred to as injection, fuel is introduced into the combustionchamber. In a process hereinafter referred to as ignition, the injectedfuel is ignited by known ignition means such as spark plug 92, resultingin combustion. During the expansion stroke, the expanding gases pushpiston 36 back to BDC. Crankshaft 40 converts piston movement into arotational torque of the rotary shaft. Finally, during the exhauststroke, the exhaust valve 54 opens to release the combusted air-fuelmixture to exhaust manifold 48 and the piston returns to TDC. Note thatthe above is shown merely as an example, and that intake and exhaustvalve opening and/or closing timings may vary, such as to providepositive or negative valve overlap, late intake valve closing, orvarious other examples.

Referring now to FIG. 2A, an example multi-cylinder engine that includestwo cylinder banks is shown. The engine includes cylinders andassociated components as shown in FIG. 1. Engine 10 includes eightcylinders 210. Each of the eight cylinders is numbered and the numbersof the cylinders are included within the cylinders. Fuel injectors 66selectively supply fuel to each of the cylinders that are activated(e.g., combusting fuel during a cycle of the engine). Cylinders 1-8 maybe selectively deactivated to improve engine fuel economy when less thanthe engine's full torque capacity is requested. For example, cylinders2, 3, 5, and 8 (e.g., a pattern of deactivated cylinders) may bedeactivated during an engine cycle (e.g., two revolutions for a fourstroke engine). During a different engine cycle, cylinders 1, 4, 6, and7 may be deactivated. Further, other patterns of cylinders may beselectively deactivated based on vehicle operating conditions.

Engine 10 includes a first cylinder bank 204, which includes fourcylinders 1, 2, 3, and 4. Engine 10 also includes a second cylinder bank202, which includes four cylinders 5, 6, 7, and 8. Cylinders of eachbank may be active or deactivated during a cycle of the engine. A firstfuel controller adjusts fuel injection timing to control amounts of fuelinjected to the first cylinder bank. A second fuel controller adjustsfuel injection timing to control amounts of fuel injected to the secondcylinder bank. The fuel controllers may be constructed as shown in FIG.3. The air-fuel ratio of the first cylinder bank may be controlledindependently from the air-fuel ratio of the second cylinder bank.

Referring now to FIG. 2B, an example multi-cylinder engine that includesone cylinder banks is shown. The engine includes cylinders andassociated components as shown in FIG. 1. Engine 10 includes fourcylinders 210. Each of the four cylinders is numbered and the numbers ofthe cylinders are included within the cylinders. Fuel injectors 66selectively supply fuel to each of the cylinders that are activated(e.g., combusting fuel during a cycle of the engine). Cylinders 1-4 maybe selectively deactivated to improve engine fuel economy when less thanthe engine's full torque capacity is requested. For example, cylinders 2and 3 (e.g., a pattern of deactivated cylinders) may be deactivatedduring an engine cycle (e.g., two revolutions for a four stroke engine).During a different engine cycle, cylinders 1 and 4 may be deactivated.Further, other patterns of cylinders may be selectively deactivatedbased on vehicle operating conditions.

Engine 10 includes a single cylinder bank 250, which includes fourcylinders 1-4. Cylinders of the single bank may be active or deactivatedduring a cycle of the engine. A fuel controller adjusts fuel injectiontiming to control amounts of fuel injected to the sole cylinder bank.The fuel controller may be constructed as shown in FIG. 3.

The system of FIGS. 1-2B provides for an engine system, comprising: anengine including one or more cylinder deactivating mechanisms; acontroller including executable instructions stored in non-transitorymemory to inject an amount of fuel to a cylinder of the engine inresponse to a fuel injection delay, the fuel injection delay based on acylinder firing schedule array when the cylinder firing schedule arrayis available, and the fuel injection delay based on a weighted averageof a fuel injection delay of a past engine cycle and a fuel injectiondelay of a present engine cycle when the firing schedule array is notavailable. The engine system includes where the fuel injection delay isprovided via adding a base fuel injection delay to the weighted average.The engine system includes where the fuel injection delay is based on abase fuel injection delay time. The engine system also includes wherethe base fuel injection delay time is a fuel injection delay time whenall engine cylinders of an engine are combusting air and fuel. Theengine system also includes where the fuel injection delay is furtherbased on an engine cycle time when the cylinder firing schedule array isavailable. The engine system further comprises additional instructionsto base the fuel injection delay on a predetermined number of delaycycles if no cylinders are scheduled to fire in a next cycle of theengine.

FIG. 3 shows a closed loop fuel control system 300 that includes a SmithPredictor (SP) control section 305 to compensate for the response delaybetween injection fuel and detection of combustion products of the fuelat the oxygen sensor (e.g., 126 of FIG. 1). The controller of FIG. 3 maybe incorporated into and may cooperate with the system of FIGS. 1, 2A,and 2B. Further, at least portions of the controller may be incorporatedas executable instructions stored in non-transitory memory while otherportions of the method may be performed via a controller transformingoperating states of devices and actuators in the physical world. The SPcontrol section 305 acts as a lead filter to compensate for the timedelay between injection of fuel and observation of fuel combustionbyproducts. The SP control section 305 includes an SP filter orprediction block 306 that is supplied a time constant from block 304 andit is connected in series with an SP delay block 310 so that the SPdelay block receives the output of the SP filter block. The SP controlsection 305 includes an inner feedback loop in which the control signaloutput from the PI controller 314 is fed back to the input of the SPfilter block 306. Block 306 uses a time constant that is a function ofengine speed and load (normalized cylinder air charge). Block 308 is afuel injection delay and the fuel injection delay applies a fuelinjection delay that is determined as described in FIGS. 4-8. Block 310implements the fuel injection delay from block 308 by delaying output ofblock 310 from the input of block 310 by the time amount requested byblock 308. The Smith Predictor provides two estimated signals: theresponse of the system with the pure delay (output of 310) and withoutit (output of 306). The Smith Predictor will allow the PI controller toessentially operate as if the actual system did not have the pure delayor is delay-free, as long as the output of the 310 and measured signalfrom oxygen sensor 126 match one another. In the case of a referencechange, assuming no disturbance and that the blocks 306 and 310 have acorrectly identified SP model of the actual system, this assumption ismet and the system will respond as if no delay existed. If a disturbanceoccurs, then the error will be detected as a difference between the SPmodel (310) and the measured (126) system, which the controller will tryto correct. In this way, the closed loop system is stabilized by thedelay compensator, so much so that higher gains can be used. Because ofthis, the controller's response to a disturbance has a peak error thatis somewhat reduced, and the duration of the error that is greatlyreduced. For the application of fuel control, this makes the delaycompensation very valuable, since it minimizes the integrated error offuel/air ratio going to the catalyst, which can only absorb a limitedamount of fuel/air deviation from stochiometry.

Block 302 represents a reference signal or desired engine air-fuel ratioor lambda (e.g., desired engine air-fuel ratio/stoichiometric air-fuelratio). Block 316 is a lambda value of one used to control the engine toa stoichiometric air-fuel mixture. Block 314 represents aproportional/integral controller. Block 10 represents the plant orengine. The outputs of blocks 302, 306, 310, 126 are summed together at312, with appropriate sign, to provide a delay compensated error signalto the PI controller 314. Output of PI controller 314 is added to avalue of one and multiplied by the reference value at block 320. Theoutput from block 320 is a value of one when a stoichiometric air-fuelratio is desired and when there is no error indicated from the oxygensensor 126. Block 322 is a model of air-fuel ratio disturbances andblock 326 is a cylinder intake wall wetting model. Output ofmultiplication block 320 is added to output of block 322 at summingjunction 324. The desired engine air-fuel ratio is provided to plant orengine 10 via adjusting fuel injection timing and the amount of fuelinjected to the engine. Oxygen sensor 126 samples exhaust gases andconverts an oxygen concentration into a measured engine air-fuel ratio.

Smith predictor 305 compensates for fuel injection delays that may limitthe amount of gain that may be applied within PI controller 314 toregulate engine air-fuel ratio. The gains of PI controller 314 may be aproportional gain K_(P) and an integral gain K_(I), which may be scalarreal numbers that multiply the error input to PI controller 314 viasumming block 312.

Referring now to FIGS. 4-6, a block diagram to determine fuel injectiontime delay of an engine that may selectively deactivate and activatecylinders to improve engine fuel economy is shown. The method of FIGS.4-6 may be incorporated into and may cooperate with the system of FIGS.1, 2A, and 2B. Further, at least portions of the method of FIGS. 4-6 maybe incorporated as executable instructions stored in non-transitorymemory while other portions of the method may be performed via acontroller transforming operating states of devices and actuators in thephysical world. Method 400 includes event based and time basedoperations as indicated below. Event based operations may be initiatedby hardware interrupts produced via an engine position sensor or asignal that is based off input from an engine position sensor. Timebased operations are initiated at predetermined time intervals scheduledby the controller. Method 400 may be part of a controller that controlsfuel delivery to one cylinder bank of an engine.

At 401, method 400 judges if a cylinder firing schedule is available. Inone example, a cylinder firing schedule is an array stored in memorythat indicates which engine cylinders will fire during an engine cycle.FIG. 8 shows one example of a cylinder firing schedule. A cylinderfiring schedule may not be available during some conditions such as ifthe controller does not include a cylinder firing schedule or if acylinder firing schedule is not present because of operating conditions.For example, a cylinder firing schedule may not be available if theengine enters a degraded state or if the cylinder firing schedule cannotbe revised at present operating conditions. If method 400 judges that acylinder firing schedule is available, the answer is yes and method 400proceeds to 402 of FIG. 5. Otherwise, the answer is no and method 400proceeds to 440 of FIG. 6.

At 402, method 400 judges if fuel is injected to a cylinder of acylinder bank controlled based on method 400 at a present cylinderinterrupt. Step 402 may be initiated by a cylinder interrupt event. Thecylinder interrupt may be generated based on a rising edge of a signalthat is based on engine position sensor output (e.g., a signal based onoutput of a crankshaft position sensor and a camshaft position sensor).An example cylinder interrupt signal is shown in FIG. 7. A cylinderinterrupt signal rising edge may be generated at 10 crankshaft degreesbefore top-dead-center compression stroke for each engine cylinderduring an engine cycle. In one example, method 400 tracks which cylinderis a latest cylinder to receive fuel via a bit or word in memory. If nofuel is injected to a cylinder of the cylinder bank being regulated bythe controller for the present cylinder interrupt, the answer is no andmethod 400 proceeds to 404. Otherwise, the answer is yes and method 400proceeds to 420.

At 420, method 400 revises two variables stored in memory. First, method400 updates variable extra_del_cnt_last to equal a value of variableextra_delay_count. The variable extra_delay_count is a value of acounter that keeps track of how many cylinder interrupts have occurredfor the cylinder bank regulated by the controller without fuel beinginjected to the cylinder bank. The variable extra_delay_count is basedon the present engine cycle. The variable extra_del_cnt_last is thevalue of the counter that keeps track of how many cylinder interruptshave occurred for the cylinder bank regulated by the controller withoutfuel being injected to the cylinder bank for a last or previous enginecycle. Thus, method 400 pushes the value of extra_delay_count intoextra_del_cnt_last when fuel is injected to a cylinder at the presentcylinder interrupt. Method 400 proceeds to 406.

At 404, method 400 increments the value of the counter stored invariable extra_delay_count by a value of one, which corresponds to onecylinder event (e.g., injection of fuel to the cylinder, oralternatively, combustion in the cylinder). Step 404 is also initiatedby the cylinder interrupt. Method 400 proceeds to 406.

At 406, method 400 converts the count values from 402 and 404 intovalues having engine cycle units. In particular, the variableextra_delay_count is converted into engine cycle units by dividingextra_delay_count by the number of cylinders per engine cylinder bank,or extra_delay_cycle=extra_delay_count/cyl_per_bank, whereextra_delay_cycle is the count of how many cylinder interrupts haveoccurred for the cylinder bank regulated by the controller without fuelbeing injected to the cylinder bank during the present engine cycle inengine cycle units. The variable extra_delay_cycle is a fractionalnumber that is rounded. The variable cyl_per_bank is the number ofcylinders within the cylinder bank being regulated by the controller.

The variable extra_del_cnt_last is converted into engine cycle units bydividing extra_del_cnt_last by the number of cylinders per enginecylinder bank, or extra_delay_cycle_last=extra_del_cnt/cyl_per_bank,where extra_delay_cycle_last is the count of how many cylinderinterrupts have occurred for the cylinder bank regulated by thecontroller without fuel being injected to the cylinder bank during thelast engine cycle in engine cycle units. The variable cyl_per_bank isthe number of cylinders within the cylinder bank being regulated by thecontroller. The Step 406 is also initiated by the cylinder interrupt.

At 408, method 400 determines the additional or extra fuel injectiondelay time associated with deactivating one or more engine cylinders ofa cylinder bank. In one example, the extra fuel injection delay time isa weighted average of present and past engine cycle fuel injectiondelays. Specifically, the extra or additional fuel injection delay timeadded to a base fuel injection delay time is given by the followingequation:extra_delay_tm=(extra_delay_cycle*(1−WA_last)+extra_delay_cycle_last*WA_last)*engine_cycle_tm,where extra_delay_tm is the fuel injection delay time, WA is a weightingaverage parameter with a value between 0 and 1, engine_cycle_tm is thetime it takes for the engine to complete two engine revolutions (or onecycle) at the present engine speed, and the other variables are aspreviously described. If the value variable WA is greater than 0.5 thelast engine cycle's extra fuel injection delay is given more weight thanthe present engine cycle's fuel injection delay. The larger value ofvariable WA, the closer the present cylinder cycle's extra fuelinjection delay will match the previous cylinder cycle's extra fuelinjection delay. If all engine cylinders are reactivated, the extra fuelinjection delay will reach a value of zero in two engine cycles nomatter the value of WA. The operations of step 408 are performed atpredetermined constant time intervals. Method 400 proceeds to 410.

At 410, method 400 retrieves a fuel injection time delay from a table inmemory. The table in memory may be indexed via present engine speed andpresent engine torque output. The table outputs an empiricallydetermined fuel injection time delay for when the engine is operatingwith all cylinders activated and combusting air and fuel. The base fuelinjection time delay occupies a variable in memory base_delay_tm. Theoperations of step 410 are performed at predetermined constant timeintervals. Method 400 proceeds to 412.

At 412, method 400 determines the total fuel injection delay time forthe present engine cycle. The total fuel injection delay time is givenby the equation: total_delay_tm=extra_delay_tm+base_delay_tm. Theoperations of step 412 are performed at predetermined constant timeintervals. Method proceeds to 414.

At 414, method 400 adjusts a fuel injection delay time (e.g., a valuestored in block 308 of FIG. 3) with the value determined at 412.Further, fuel injection timing adjustments are applied to timing of fuelinjectors of a cylinder bank so that the amount of fuel injected toengine cylinders is adjusted responsive to the fuel injection delay timeas describe in FIG. 3. Method 400 proceeds to exit.

In this way, fuel injection delay may be adjusted even if a cylinderfiring schedule array is not available. The fuel injection delay timemay allow proportional and integral gain values of a fuel controller tobe increased without causing the fuel control system to oscillate fueldelivery.

At 440, method 400 queries a cylinder firing schedule array stored inmemory. In one example, the array may include a predetermined number ofcells that correspond to the number of engine cylinders. Cells in thearray are populated with values that correspond to engine cylindernumbers or a value of zero. A value of zero indicates that no cylinderfires for the cylinder event associated with the cell in the array forthe present engine cycle. A cylinder firing array for a four cylinderengine may be constructed as follows:

Cell 1 Cell 2 Cell 3 Cell 4 1 3 4 2where the array cells are outlined in bold. The first cell in the arrayis populated with a value of 1 to indicate cylinder number one is thefirst cylinder to fire (e.g., combust air and fuel) during the enginecycle. The second cell in the array is populated with a value of 3 toindicate cylinder number three is the second cylinder to fire during theengine cycle. The third cell in the array is populated with a value offour to indicate that cylinder number four is the third cylinder to fireduring the engine cycle. The fourth cell in the array is populated witha value of two to indicate cylinder number two is the fourth cylinder tofire during the engine cycle. The array cells correspond to a firingorder for the engine. For example, where the four cylinder engine has afiring order of 1, 3, 4, 2 the first array cell from left to right isthe array cell for cylinder number one. The second array cell from theleft to right is the array cell for cylinder number three, and so on.

Of course, cylinder firing schedule arrays may be constructed inalternative ways. For example, cylinder firing arrays may only containvalues of one and zero where the particular cells of the array areassigned to selected engine cylinders.

Method 400 logs or stores to memory cylinders that will fire during thepresent engine cycle for the cylinder bank having fuel controlled by thepresent method. In the above example, the engine includes a single bankand all four cylinders are logged to memory as cylinders that will fireduring the present engine cycle. Step 440 is initiated by a cylinderinterrupt event. Method 400 proceeds to 442.

At 442, method 400 judges if fuel is injected to a cylinder of acylinder bank controlled based on method 400 at a present cylinderinterrupt according to values in the array evaluated at 440. Step 442may be initiated by a cylinder interrupt event. If method 400 judgesthat a cylinder of the cylinder bank is to receive fuel and combust thefuel during the present engine cycle, the answer is yes and method 400proceeds to 444. Otherwise, the answer is no and method 400 proceeds to460.

At 460, method 400 revises one variables stored in memory. Method 400updates variable extra_delay_cycle to equal a value of variablemax_extra_delay. The value of variable max_extra_delay is set to a valueof between 1 and 1.5 (cycles). This value limits the fuel injectiondelay estimate to a reasonable value. Method 400 proceeds to 448.

At 444, method 400 examines the cylinder firing array and determines thecylinder in the array to receive the fuel being currently computed.Then, method 400 counts cylinder firing array cells until a cell isreached where fuel is injected and the count is stored to memory. Forexample, using the firing array above, if the cylinder to receive fuelis cylinder three as indicated by the second cell in the array movingfrom left to right, then the count is a value of one when it isdetermined that the next cylinder to receive fuel is cylinder numberfour as indicated by the third cell in the array. However, if the valuein cell three is zero, the count increased to a value of two and stopswhen it is found that cylinder number two receives fuel based on thevalue in the fourth cell. Method 400 proceeds to 446.

At 446, method 400 converts the count values from 402 and 404 intovalues having engine cycle units. In particular, the count from step 444is converted into engine cycle units by dividing the variable count bythe number of cylinders per engine cylinder bank, orextra_delay_cycle=(count−1)/cyl_per_bank, where count is the count ofhow many cylinder events (e.g., cells in the cylinder firing schedulearray) are there ahead of the present cylinder event where fuel is notinjected to cylinders of the cylinder bank. The variable cyl_per_bank isthe number of cylinders within the cylinder bank being regulated by thecontroller. Method 400 proceeds to 448.

At 448, method 400 determines the additional or extra fuel injectiondelay time associated with deactivating one or more engine cylinders ofa cylinder bank. In one example, the extra fuel injection delay time isdetermined by the following equation:extra_delay_tm=extra_delay_cycle*engine_cycle_tm, where extra_delay_tmis the fuel injectin delay time and engine_cycle_tm is the time it takesfor the engine to complete two engine revolutions (or one cycle) at thepresent engine speed. The operations of step 448 are performed atpredetermined constant time intervals. Method 400 proceeds to 450.

At 450, method 400 retrieves a fuel injection time delay from a table inmemory. The table in memory may be indexed via present engine speed andpresent engine torque output. The table outputs an empiricallydetermined fuel injection time delay for when the engine is operatingwith all cylinders activated and combusting air and fuel. The base fuelinjection time delay occupies a variable in memory base_delay_tm. Theoperations of step 450 are performed at predetermined constant timeintervals. Method 400 proceeds to 452.

At 452, method 400 determines the total fuel injection delay time forthe present engine cycle. The total fuel injection delay time is givenby the equation: total_delay_tm=extra_delay_tm+base_delay_tm. Theoperations of step 452 are performed at predetermined constant timeintervals. Method proceeds to 454.

At 454, method 400 adjusts a fuel injection delay time (e.g., a valuestored in block 308 of FIG. 3) with the value determined at 452.Further, fuel injection timing adjustments are applied to timing of fuelinjectors of a cylinder bank so that the amount of fuel injected toengine cylinders is adjusted responsive to the fuel injection delay timeas describe in FIG. 3. Method 400 proceeds to exit.

In this way, fuel injection delay may be adjusted based on a knowncylinder firing schedule so that the fuel injection delay time may bemore precisely determined. The fuel injection delay time may allowproportional and integral gain values of a fuel controller to beincreased without causing the fuel control system to oscillate fueldelivery.

Thus, the method of FIG. 5 provides for an engine control method,comprising: injecting fuel to an engine via a controller in response toa fuel injection delay produced via a weighted average of a fuelinjection delay of a past engine cycle and a fuel injection delay of apresent engine cycle. The method includes where the fuel injection delayis estimated without a cylinder firing schedule of a cylinder cycle. Themethod includes where estimating the fuel injection delay also includesadding a base fuel injection delay to the weighted average.

In some examples, the method includes where the base fuel injectiondelay is a fuel injection delay time when all engine cylinders of anengine are combusting air and fuel. The method includes where the fuelinjection delay of the present engine cycle is based on a value of acounter that is incremented in response to absence of injecting fuel toa cylinder of an engine bank during a prescribed crankshaft angularinterval of the present engine cycle. The method also includes where thefuel injection delay of the past engine cycle is based on a value of acounter that is incremented in response to absence of injecting fuel toa cylinder of an engine bank during a prescribed crankshaft angularinterval of a past engine cycle. The method further comprisescompensating for the fuel injection delay via a fuel controller includedin the controller.

The method of FIG. 6 provides for an engine control method, comprising:injecting fuel to an engine via a controller in response to a fuelinjection delay produced via adding a base cylinder delay time and anextra delay time, the base cylinder delay time a first delay time forthe engine when all cylinders of the engine are firing in a first cycleof the engine, the extra delay time a second delay time for the enginewhen less than all cylinders of the engine are firing in a second cycleof the engine. The method includes where the extra delay is produced viamultiplying an actual total number of delay cycles by an engine cycletime. The method includes where the engine cycle time is a time it takesthe engine to rotate two engine revolutions at a present speed of theengine. The method includes where the actual total number of delaycycles is based on a counter. The method also includes where the actualtotal number of delay cycles is based on a cylinder firing schedulearray.

In some examples, the method further comprises compensating for the fuelinjection delay via a fuel controller included in the controller. Themethod further comprises basing the extra delay time on a predeterminednumber of delay cycles when no cylinders are scheduled to fire during anext engine cycle.

Referring now to FIG. 7, an example sequence that shows how fuelinjection delay time may be determined when a cylinder firing schedulearray is not available. The sequence of FIG. 7 may be provided accordingto the method of FIG. 5. The plots shown in FIG. 7 occur at the sametime and are aligned in time.

The first plot from the top of FIG. 7 is a plot of a cylinder interruptsignal state versus time. The cylinder interrupt signal is comprised ofa series of pulses having a high level and a low level. The positiverising edges 702 of the signals may be part of a hardware interrupt thatinitiates control actions described in method 400. Each pulse of thetrace corresponds to a cylinder number that is associated with thecylinder interrupt. For example, pulse 750 is a cylinder interrupt forcylinder number three. The rising edge 702 of the interrupt for cylindernumber three may be at a prescribed engine position (e.g., 10 crankshaftdegrees before top-dead-center compression stroke for cylinder numberthree). The rising edges of the cylinder interrupts correspond tosimilar engine positions for the other engine cylinders. The cylinderinterrupt signal may be provided based on output of a crankshaftposition sensor and output of a camshaft position sensor. The verticalaxis represents cylinder interrupt state and the horizontal axisrepresents time. Time increases from the left side of the plot to theright side of the plot.

The second plot from the top of FIG. 7 is a plot of fuel injectionevents versus time. The vertical axis indicates fuel injection eventstate and fuel is being injected when the trace is at a higher levelnear the vertical axis arrow. Fuel is not being injected when the traceis at a lower level near the horizontal axis. In this example, fuel fora cylinder receiving fuel occurs before the cylinder interrupt for thecylinder receiving fuel. For example, the fuel injected at 752 isinjected to cylinder number three. Thus, the fuel injection into acylinder leads the cylinder interrupt rising edge for that cylinder inthis example. Time increases from the left side of the plot to the rightside of the plot.

The third plot from the top of FIG. 7 is a plot of a fuel injectiondelay counter value versus time. The vertical axis indicates the valueof the fuel injection delay count (e.g., the value of variableextra_delay_count from FIG. 5) and the fuel injection delay countincreases in the direction of the vertical axis arrow. Time increasesfrom the left side of the plot to the right side of the plot.

The fourth plot from the top of FIG. 7 is a plot of a fuel injectiondelay time value versus time. The vertical axis indicates the value ofthe fuel injection delay time (e.g., the value of variableextra_delay_tm from FIG. 5) and the fuel injection delay count increasesin the direction of the vertical axis arrow. Time increases from theleft side of the plot to the right side of the plot.

At time T0, the cylinder interrupt state is at a low value and fuel isnot being injected. The fuel injection delay count value is zero and theextra delay time is also zero. Fuel is injected to cylinder number onebetween time T0 and time T1.

At time T1, the rising edge of the cylinder interrupt signal occurs andan inquiry is made to determine if fuel was injected. Since fuel wasinjected between time T0 and time T1, the fuel injection delay countremains at zero since no fuel injection delay is induced viadeactivating a cylinder. The extra delay time also remains at zero.

Between time T1 and time T2, fuel is injected two more times and twoadditional cylinder interrupts occur. The delay count value and extradelay time remain at values of zero. Fuel is not injected between theinterrupt for cylinder number four and the interrupt for cylinder numbertwo at time T2.

At time T2, the interrupt for cylinder number two occurs, but fuel wasnot injected to cylinder number two as indicated by the absence of afuel injection pulse between the rising edge of cylinder number fourinterrupt and the rising edge of cylinder number two interrupt at timeT2. Therefore, the value of the fuel injection delay count is increasedby a value of one. Further, the value of the fuel injection delay timeis increased based on the value of the fuel injection delay count asdescribed in FIG. 5.

Between time T2 and time T3, fuel is injected to cylinder number one.The fuel injection delay counter value remains at a value of one and theextra delay time is a value greater than zero.

At time T3, the cylinder interrupt for cylinder number one occurs whichcauses the fuel injection counter to update. Since fuel was injected tocylinder number one, the fuel injection counter value is changed to zeroand the extra delay time is changed to zero.

Between time T3 and time T4, fuel is not injected to cylinder numberthree. The fuel injection delay counter value remains at a value of zeroand the extra delay time is a value of zero.

At time T4, the interrupt for cylinder number three occurs, but fuel wasnot injected to cylinder number three as indicated by the absence of afuel injection pulse between the rising edge of cylinder number oneinterrupt and the rising edge of cylinder number three interrupt at timeT4. Therefore, the value of the fuel injection delay count is increasedby a value of one. Further, the value of the fuel injection delay timeis increased based on the value of the fuel injection delay count asdescribed in FIG. 5.

Between time T4 and time T5, fuel is not injected to cylinder numberfour. The fuel injection delay counter value remains at a value of oneand the extra delay time is a value greater than zero.

At time T5, the interrupt for cylinder number four occurs, but fuel wasnot injected to cylinder number four as indicated by the absence of afuel injection pulse between the rising edge of cylinder number threeinterrupt and the rising edge of cylinder number four interrupt at timeT5. Therefore, the value of the fuel injection delay count is increasedto a value of two. Further, the value of the fuel injection delay timeis increased again based on the value of the fuel injection delay countas described in FIG. 5. The fuel injection delay and extra delay timeare returned back to values of zero at the next cylinder interrupt forcylinder number 3 since fuel is injected to cylinder number two.

In this way, values of the fuel injection delay time and extra delaytime may be adjusted based on observed fuel injection and cylinderinterrupts. Knowledge of a cylinder firing schedule array is not used todetermine the fuel injection delay time.

Referring now to FIG. 8, an example sequence that shows how fuelinjection delay time may be determined when a cylinder firing schedulearray is available. The sequence of FIG. 8 may be provided according tothe method of FIG. 6. The plots shown in FIG. 8 occur at the same timeand are aligned in time.

The first plot from the top of FIG. 8 is a plot of a cylinder interruptsignal state versus time. The cylinder interrupt signal is comprised ofa series of pulses having a high level and a low level. The positiverising edges 802 of the signals may be part of a hardware interrupt thatinitiates control actions described in method 400. Each pulse of thetrace corresponds to a cylinder number that is associated with thecylinder interrupt. For example, pulse 820 is a cylinder interrupt forcylinder number three. The rising edge 802 of the interrupt for cylindernumber three may be at a prescribed engine position (e.g., 10 crankshaftdegrees before top-dead-center compression stroke for cylinder numberthree. The rising edges of the cylinder interrupts correspond to similarengine positions for the other engine cylinders. The cylinder interruptsignal may be provided based on output of a crankshaft position sensorand output of a camshaft position sensor. The vertical axis representscylinder interrupt state and the horizontal axis represents time. Timeincreases from the left side of the plot to the right side of the plot.

The second plot from the top of FIG. 8 is a plot of cylinder firingschedule array versus time. The vertical axis indicates cylinder firingschedule array. The cylinder firing arrays 804 are updated once eachengine cycle (e.g., two engine revolutions). In this example, thecylinder firing array is updated before the cylinder interrupt forcylinder number one. The cylinder firing array describes which cylindersreceive fuel during the engine cycle as previously described. Zeros inthe array indicate no fuel injection for the cylinder associated withthe array cell. The horizontal axis represents time and time increasesfrom the left side of the plot to the right side of the plot.

The third plot from the top of FIG. 8 is a plot of an extra_delay_cyclevalue versus time. The vertical axis indicates the value of theextra_delay_cycle variable (e.g., the value of variableextra_delay_cycle from FIG. 6) and the extra_delay_cycle value increasesin the direction of the vertical axis arrow. The horizontal axisrepresents time and time increases from the left side of the plot to theright side of the plot.

The fourth plot from the top of FIG. 8 is a plot of a fuel injectiondelay time value versus time. The vertical axis indicates the value ofthe fuel injection delay time (e.g., the value of variableextra_delay_tm from FIG. 6) and the fuel injection delay count increasesin the direction of the vertical axis arrow. The horizontal axisrepresents time and time increases from the left side of the plot to theright side of the plot.

At time T10, the cylinder interrupt state is low and the cylinder firingschedule is populated with values to indicate that all engine cylinderswill fire during the present engine cycle. The extra_delay_cycle valueis zero and the extra delay time is zero.

At time T11, the cylinder interrupt for cylinder number one occurs. Fuelwas injected to cylinder number one as indicated by cell 850 of thecylinder firing schedule array and the counter that counts cylinders notreceiving fuel increases to a value of one (not shown) when it evaluatescell 852. But, since cell 852 indicates fuel is injected to the nextcylinder in the firing order for the cylinder bank, the count stops atone. Counting begins at the cylinder firing schedule array cell thatcorresponds to the present cylinder interrupt and ends at the cell wherefuel injection is indicated. In this example, the counting starts fromcell 850 and ends at cell 852. The extra delay cycle variable is a valueof zero since the extra delay cycle calculation subtracts a value of onefrom the cycle counter. The extra delay time also remains at a value ofzero since the extra delay cycle value is zero.

Between time T11 and time T12, several cylinder interrupts occur.However, since fuel is injected to cylinders, the extra delay cycle andextra delay time remain at zero. Shortly before time T12, the cylinderfiring schedule array is updated and fuel is not injected to cylindernumber three for this engine cycle as indicated by the value of zero incell 862,

At time T12, the cylinder interrupt for cylinder number one occurs. Fuelwas injected to cylinder number one as indicated by cell 860 of thecylinder firing schedule array and the counter that counts cylinders notreceiving fuel increases to a value of one (not shown) when it evaluatescell 862. But, since cell 862 indicates fuel is not injected to the nextcylinder in the firing order for the cylinder bank, the count is a valueof one and the counting continues to cell 864 where it is increased to avalue of two and stopped because fuel injection is indicated again inthe third cell. The extra delay cycle variable is increased to a valueof one since the extra delay cycle calculation subtracts a value of onefrom the cycle counter which is a value of two at this point. The extradelay time increases in response to the extra delay cycle valueincreasing.

At time T13, the cylinder interrupt for cylinder number three occurs.Fuel was not injected to cylinder three as indicated by cell 862 of thecylinder firing schedule array, but the counter that counts cylindersnot receiving fuel finds that fuel is delivered to cylinder number fourat cell 864. Counting from cell 862, the counter increases to a value ofone at cell 864 and then it stops because fuel is indicated as beinginjected. Therefore, the extra delay cycle value is zero and the extradelay time is zero.

Between time T13 and time T14, fuel is injected to each cylinder of thecylinder bank (the four cylinder engine has only one bank of cylinders),so the extra delay count and extra delay time remain at zero.

At time T14, the cylinder interrupt for cylinder number three occurs.Fuel was injected to cylinder number three as indicated by cell 870 ofthe cylinder firing schedule array and the counter that counts cylindersnot receiving fuel increases to a value of one (not shown) when itevaluates cell 872. But, since cell 872 indicates fuel is not injectedto the next cylinder in the firing order for the cylinder bank, thecount is a value of one and the counting continues to cell 874 where itis increased to a value of two and stopped because fuel injection isindicated again in the fourth cell. The extra delay cycle variable isincreased to a value of one since the extra delay cycle calculationsubtracts a value of one from the cycle counter which is a value of twoat this point. The extra delay time increases in response to the extradelay cycle value increasing.

At time T15, the cylinder interrupt for cylinder number four occurs.Fuel was not injected to cylinder four as indicated by cell 872 of thecylinder firing schedule array, but the counter that counts cylindersnot receiving fuel finds that fuel is delivered to cylinder number twoat cell 874. Counting from cell 872, the counter increases to a value ofone at cell 874 and then it stops because fuel is indicated as beinginjected. Therefore, the extra delay cycle value is zero and the extradelay time is zero.

In this way, fuel injection delay time may be revised responsive tovalues in a cylinder firing schedule array so that the fuel injectiondelay may be based on known instances of cylinder deactivation whichmodifies the fuel injection delay time. As such, fuel injection timingdelays may be based on an actual engine combustion sequence.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, atleast a portion of the described actions, operations and/or functionsmay graphically represent code to be programmed into non-transitorymemory of the computer readable storage medium in the control system.The control actions may also transform the operating state of one ormore sensors or actuators in the physical world when the describedactions are carried out by executing the instructions in a systemincluding the various engine hardware components in combination with oneor more controllers.

This concludes the description. The reading of it by those skilled inthe art would bring to mind many alterations and modifications withoutdeparting from the spirit and the scope of the description. For example,I3, I4, I5, V6, V8, V10, and V12 engines operating in natural gas,gasoline, diesel, or alternative fuel configurations could use thepresent description to advantage.

1. An engine control method, comprising: injecting fuel to an engine viaa controller in response to a fuel injection delay produced via aweighted average of a past fuel injection delay of a past engine cycleand a present fuel injection delay of a present engine cycle.
 2. Themethod of claim 1, where the fuel injection delay is estimated without acylinder firing schedule of a cylinder cycle.
 3. The method of claim 1,where estimating the fuel injection delay also includes adding a basefuel injection delay to the weighted average.
 4. The method of claim 3,where the base fuel injection delay is based on when all enginecylinders of an engine are combusting air and fuel.
 5. The method ofclaim 1, where the present fuel injection delay of the present enginecycle is based on a value of a counter that is incremented in responseto absence of injecting fuel to a cylinder of an engine bank during aprescribed crankshaft angular interval of the present engine cycle. 6.The method of claim 1, where the past fuel injection delay of the pastengine cycle is based on a value of a counter that is incremented inresponse to absence of injecting fuel to a cylinder of an engine bankduring a prescribed crankshaft angular interval of a past engine cycle.7. The method of claim 1, further comprising compensating for the fuelinjection delay via a fuel controller included in the controller.
 8. Anengine control method, comprising: injecting fuel to an engine via acontroller in response to a fuel injection delay produced via adding abase cylinder fuel injection delay time and an extra fuel injectiondelay time, the base cylinder fuel injection delay time a first delaytime for the engine when all cylinders of the engine are firing in afirst cycle of the engine, the extra fuel injection delay time a seconddelay time for the engine when less than all cylinders of the engine arefiring in a second cycle of the engine.
 9. The method of claim 8, wherethe extra fuel injection delay is produced via multiplying an actualtotal number of delay cycles by an engine cycle time.
 10. The method ofclaim 9, where the engine cycle time is a time it takes the engine torotate two engine revolutions at a present speed of the engine.
 11. Themethod of claim 9, where the actual total number of delay cycles isbased on a counter.
 12. The method of claim 9, where the actual totalnumber of delay cycles is based on a cylinder firing schedule array. 13.The method of claim 8, further comprising compensating for the fuelinjection delay via a fuel controller included in the controller. 14.The method of claim 8, further comprising basing the extra fuelinjection delay time on a predetermined number of delay cycles when nocylinders are scheduled to fire during a next engine cycle.
 15. Anengine system, comprising: an engine including one or more cylinderdeactivating mechanisms; a controller including executable instructionsstored in non-transitory memory to inject an amount of fuel to acylinder of the engine in response to a fuel injection delay, the fuelinjection delay based on a cylinder firing schedule array when thecylinder firing schedule array is available, and the fuel injectiondelay based on a weighted average of a fuel injection delay of a pastengine cycle and a fuel injection delay of a present engine cycle whenthe firing schedule array is not available.
 16. The engine system ofclaim 15, where the fuel injection delay is provided via adding a basefuel injection delay to the weighted average.
 17. The engine system ofclaim 15, where the fuel injection delay is based on a base fuelinjection delay time.
 18. The engine system of claim 17, where the basefuel injection delay time is a fuel injection delay time when all enginecylinders of an engine are combusting air and fuel.
 19. The enginesystem of claim 18, where the fuel injection delay is further based onan engine cycle time when the cylinder firing schedule array isavailable.
 20. The engine system of claim 15, further comprisingadditional instructions to base the fuel injection delay on apredetermined number of delay cycles if no cylinders are scheduled tofire in a next cycle of the engine.